1. Field of the Invention
The present invention relates to an image forming apparatus comprising a developer apparatus which supplies developer to an image bearing body.
2. Description of the Related Art
An image forming apparatus forms a toner image that follows an electrostatic latent image on a photosensitive drum, on the circumferential surface of the photosensitive drum, by supplying a developer from a developing roller to the circumferential surface of the photosensitive drum. In the image forming apparatus disclosed in Japanese Patent Application Laid-open No. H10-55110, a developer apparatus rocks about a rocking shaft, and the posture thereof is thus changed between a developing posture in which a developing roller abuts against an image bearing body, such as a photosensitive drum, and a non-developing posture in which the developing roller is separated from the photosensitive drum. This change in the posture of the developer apparatus is carried out by driving a drive mechanism. In development processing for forming a toner image on the circumferential surface of a photosensitive drum, the posture of the developer apparatus is set to the developing posture by driving the drive mechanism. On the other hand, when not bearing out a development process, the posture of the developer apparatus is changed to the non-developing posture by reverse driving of the drive mechanism.
In an image forming apparatus of this kind, an installation structure is employed for installing and removing the developer apparatus to and from a predetermined frame, from above. Generally, this installation structure comprises a pair of U-shaped grooves which are formed respectively in mutually opposing fashion on opposite side faces of the frame, and fulcrum shafts provided respectively on the frame body of the developer apparatus so as to correspond to the U-shaped grooves. By fitting the fulcrum shafts down into the U-shaped grooves via the upper openings, the developer apparatus is installed at a predetermined position on the frame.
In the installation structure described above, when the developing roller or the agitating roller starts to rotate in a state where the posture of the developer apparatus is set to the developing posture, then in response to this rotation, the fulcrum shafts which have been fitted into the U-shaped grooves may be caused to rise upwards. If the developing roller rises up in this way, then a deviation occurs in the positional relationship between the circumferential surface of the developing roller and the circumferential surface of the photosensitive drum. As a result, the supply of toner from the developing roller to the photosensitive drum is not carried out properly, and this leads to a problem in that image defects occur.